Browsing by Author "Zedaker, Shepard M."
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- An analysis of correlated curve trend experiments in Eucalyptus grandisBredenkamp, Brian Victor (Virginia Polytechnic Institute and State University, 1988)Correlated curve trend (C.C.T.) experiments in Eucalyptus grandis on the Zululand coast of South Africa were analyzed. Growth parameters were described as functions of age using Schnute’s generalized growth function and parameter estimates were described as functions of stand density. Growth attributes were used as moments of a probability density function to describe a diameter distribution model for the species. Time trends in the relationships between growth parameters and stand density were scrutinized with multiple comparisons of paired means. It was shown that diameter growth in lower size classes ceases under conditions of extreme suppression while growth continues unabated in the larger size classes, resulting in greater dispersion in diameter. Competition mortality was to a large extent confined to the lower size classes and severe mortality results in an apparent increase in mean diameter which precludes use of growth functions which impose an asymptote. Allometric growth was investigated on two different sites and growth trends were shown to be anamorphic between sites. This permits a ratio approach to the estimation of growth and yield on one site based on experimental evidence from another. Thinning effects in terms of diameter and height changes were estimated from simulated thinnings using data from unthinned stands while the results of long-term thinning studies were compared in terms of cumulative volume yields. The age at which mean annual increment culminates was determined and a model for the estimation of m.a.i. as a function of age and stand density was constructed. A critical examination of spacing indices revealed that the slopes thereof were much steeper than those for many other species. The better-known indices of Reineke and Yoda were found to be dependent on age.
- Applications of ecological modeling in managing Central Appalachian upland oak stands for old-growth characteristicsGrinter, Lawton E. (Virginia Tech, 2002-08-06)Old-growth forests provide important habitat for wildlife, support the maintenance of biodiversity and serve as control areas for scientific research. Expanding current old-growth stand area by utilizing neighboring younger, managed stands allows private landowners to meet management needs and enables government agencies and private conservation organizations to meet old-growth forest objectives. Seven old-growth upland oak stands and seven adjacent younger, managed stands of the same site and stand type were measured in the Ridge and Valley, Blue Ridge, and Piedmont provinces of Virginia and Pennsylvania in an effort to characterize species composition, diameter distribution and canopy structure. A computer-based ecosystem/gap model (JABOWA-3) was modified and used to simulate silvicultural manipulations in the younger stands that would reproduce older forest characteristics. Various silvicultural techniques were used to convert the primarily even-aged younger stands into uneven-aged stands and then into old-growth. These manipulations included single-tree selection, herbicide application, culling larger diameter stems and planting seedlings where required. Individual trees within each of the younger, managed stands were removed at various time intervals and these simulated stands were then projected to a point in time in which the stand approximated the diameter distribution and composition of its paired old-growth stand. Several projections were made in each of the younger stands to meet this objective. Once a satisfactory projection was made for conversion of a younger stand to old-growth, a success rate was determined to gauge how close the simulated stand approximated the diameter distribution and composition of its old-growth counterpart. From this information, biologically feasible and environmentally sound management plans were created to carry out the silvicultural manipulations required by the model for each of the sites.
- Assessment of Genetic Variation of Acer rubrum L. and Liriodendron tulipifera L. Populations in Unmanaged Forests of the Southeast United StatesKovach, Katherine Elizabeth (Virginia Tech, 2008-12-01)Acer rubrum L. and Liriodendron tulipifera L. are prolific throughout their ranges in the Southeastern U.S. and also have increasingly important roles in forestry and wood products in this region. The relatively low density and intermediate strength of the wood makes them versatile for use in many different wood products. Exploring the genetic structure of these species could provide a foundation for further genetic and breeding exploration with these economically important trees. This study utilizes amplified fragment length polymorphism to determine the level of genetic diversity of these species in contrasting physiographic provinces. AFLP was performed using five primer combinations on samples collected from six unmanaged populations of each species in the Mountains and Coastal Plain of the Southeastern U.S. Wood density was determined using an X-ray densitometer. A. rubrum lacked strong genetic structure while L. tulipifera showed differentiation between physiographic provinces. Genetic diversity of A. rubrum was lower within the Mountain populations (He: 0.327) than the Coastal Plain populations (He: 0.365). The average wood density for A. rubrum is lower in the Mountains (539.00 kg/m^3) than in the Coastal Plain (575.43 kg/m^3). Genetic diversity of L. tulipifera was higher overall (He: 0.289) than within the Mountain populations (He: 0.281) or the Coastal Plain populations (He: 0.271). The average wood density for L. tulipifera is greater in the Mountains (445.45 kg/m^3) than in the Coastal Plain (441.67 kg/m^3).
- Basal Area Growth and Crown Dynamics in a Loblolly Pine Spacing TrialRadtke, Philip J. (Virginia Tech, 1996-08-02)Relationships between the culmination of basal area growth and degree of crown closure in loblolly pine (Pinus taeda L.) were investigated. A spacing trial established on the low Appalachian Piedmont and Atlantic Coastal Plain provided the data for the investigation. Test plots were planted at densities ranging from 303 to 2723 stems per acre, and at various rectangular and square spacings. Annual stem and crown measurements were used to derive the sought-after relationships. The age of basal area culmination was found to be inversely related to both planting density and site index. Crown closure was advanced on sites of relatively high quality, exhibiting an approximately linear increase with time from planting until the age of basal area culmination. The slope of this trend increased with planting density. The degree of crown closure at the age of basal area culmination was significantly higher on narrowly-spaced plots than it was on widely-spaced plots; however, it did not vary significantly with site index. Although crown closure is generally accelerated on high quality sites, the relatively early culmination of basal area growth on such sites offsets the increase - the net result being that crown closure at culmination age does not vary significantly with site differences. Crown closure indices can be used to determine whether or not a stand has reached the culmination of basal area growth; however, more readily available information on spacing and site index can be used to make the same prediction. The results of this study might be most useful to modelers of early stand dynamics in loblolly pine and other commercially important pines.
- Biochar in Land Reclamation, Biosolids Applications and Prescribed FiresFields-Johnson, Christopher Warren (Virginia Tech, 2016-12-01)Biochar is a form of stable organic carbon whose application to soils has the potential to sequester large amounts of atmospheric CO2 while improving the physical, chemical and biological properties of soil. However, the optimal rates and methods of biochar application are unknown for many situations. Three experiments were performed to test methods of biochar application to soils as a stand-alone amendment, in combination with biosolids as a complementary amendment and in-situ through controlled landscape burning. The first was a greenhouse pot study, which involved combining biochar with spoil from an Appalachian surface coal mine to grow trees. Biochar combined with mine soil produced a much higher growth rate for trees, and pure biochar helped tree root growth, suggesting that it might be useful as a broadcasted amendment, as a nursery growing medium or as a backfill in tree planting holes. The second experiment explored methods to combine biochar and biosolids materials to form a granular product. Combining biochar and biosolids before applications reduced windborne losses of biochar as well as the nutrient leachate produced by the biosolids. Drum rolling was found to work best for producing aggregate granules. Wetting pure biochar to 100% gravimetric water content before applications reduced windborne losses from over 50% to under 5% as compared to when it was applied as a dry product. A series of controlled burns were conducted in the third experiment to determine the ideal range of meteorological conditions to produce the highest possible biochar yields in-situ. Relative humidity, forest litter moisture and ambient temperature were found to be the governing factors over the tonnage of biochar produced. Up to 3.0 Mg Ha-1 of biochar were produced under ideal conditions by controlled burning. Repeated high-yielding burns have the potential accumulate large amounts of biochar in the soil to improve soil properties.
- Characterization of Vascular Plant Species Composition and Relative Abundance in Southern Appalachian Mixed-Oak ForestsHammond, Daniel N. Jr. (Virginia Tech, 1997-12-16)Eight study sites were established in mid-elevation, south aspect, mixed-oak forests in the Ridge and Valley and Allegheny Mountain physiographic provinces of Southwestern Virginia and West Virginia to address questions concerning the variability in species composition, richness, and relative abundance of vascular plant species in those communities. All forest strata were sampled using a nested plot design. Variability in species richness and species composition was found to be high. Total species richness values ranged from 84 to 273, and Sorrenson's Coefficient of Similarity index values indicated that approximately 46, 38, and 51 percent of the species in the overstory, mid-story, and herb stratum were the same among sites, respectively. However, despite differences in composition and richness, K-S tests revealed significant differences in the distribution of ranked relative abundance only in the mid-story at two sites. Differences did occur in the relative abundance of twelve growth form categories. While tree seedlings and perennial herbs dominated, on average, woody vines and fern species represented substantial coverage on sites in the Allegheny Mountains. Correlations among forest strata were weak. The greatest amount of variation in species richness was attributiable to the standard deviation of a forest site quality index (FSQI), which was thought to represent the variation in microtopography across each site. The lack of correlation and high variability in plant species richness and composition, despite similarities in topographic characteristics, reinforce the inherent weaknesses involved with using the chronosequence approach to studying ecological responses in the Southern Appalachian mixed-oak region. Future remeasurement and long term monitoring of these study sites, following the implementation of silvicultural manipulations, will provide the information needed to make inference on the effects of forest management practices on Southern Appalachian mixed-oak forests.
- Compression wood formation in Pinus strobus L. following ice storm damage in southwestern VirginiaHook, Benjamin Austin (Virginia Tech, 2010-04-22)To evaluate the compression wood response in eastern white pine (Pinus strobus L.) following a severe ice storm in 1994, 47 trees were felled in 2007 and cross-sectional samples were collected at 0.5 (±0.2) m stem height. The disks were sanded and digitally scanned, and the cross-sectional area (mm2) of compression wood within each tree-ring was quantified using image analysis software. Topographic data (slope, aspect, and elevation) were also recorded for each P. strobus tree, along with a modified competition index. Wood anatomical features were also quantified in the three years before and after the storm along a tree diameter gradient. Although tree age was relatively constant in this stand, tree size was influenced by topographic position; larger trees grew in the valley while smaller trees were found growing in thin soils at the mid-slope position. When the cohort was about 25 years old, ice deposition caused a heterogeneous compression wood response which was highly related to tree size. In the thirteen years following the ice storm, the 6 – 9 cm (2007) diameter class formed significantly more compression wood area than any other, followed by the 10 – 13 cm (2007) diameter class. The tree diameter range that formed the most post-storm compression wood was 4 – 8 cm at the time of the storm, suggesting that this diameter range was most affected by 8.5 cm of ice loading in P. strobus. Trees > 18 cm in 1994 did not form any compression wood after the storm, but many experienced a growth release to fill canopy gaps. Topographic variables did not influence compression wood formation directly, but only one plot was sampled so these results are tenuous. However, topography did influence tree size which was the most important predictor in compression wood. There was no relationship between compression wood area and competition index. Due to compression wood formation after the ice storm, cell wall thickness and cell circularity were significantly higher in the 1994 tree-ring than in other rings examined (1991 – 1993, 1995, and 1996). Tracheid and lumen diameters were significantly smaller in compression wood cells (30.5 and 19.5 μm, respectively) than in normal wood (36.8 and 28.4 μm, respectively); opposite wood cells were intermediate in size (32.4 and 24.4 μm, respectively). Due to small tracheid size, compression wood contained significantly more cells mm⁻¹ (33) than normal wood (27), but no significant differences in cell wall area. Therefore, cumulative cell wall area occupied 47% of the cross-section in compression wood tissue on average, compared to 31% in normal wood. Dispersing tree weight across a greater surface area may help compression wood to prop up a bent tree, but reduced lumen area may also impact hydraulic conductivity in the stem.
- A description of floral diversity in the southern Appalachians with forest management considerations for conservationBrown, Maryfrances McGrath (Virginia Tech, 1994-05-04)Biological diversity is the variety of plant and animal life, habitats and ecosystems, and the biological processes and functions within them. It is this simple yet profoundly important concept in biology which in recent years has become an issue of great concern to the lay public and scientific community alike. The cause for this concern lies in the current rapid destruction and transformation of many ecosystems worldwide. From temperate and tropical rain forests to coral reefs, the loss of habitat due to the pressures of an expanding human population threatens the existence of numerous species of plants and animals. It is suspected that thousands of species of plants and animals are being lost before ever being described, let alone tested for their usefulness as medicines or crops (Wilson 1988). Over 25% of prescription drugs available today contain active compounds that are extracted directly from plants (Ledig 1988). In addition, the cross breeding of domesticated crop species with wild relatives has resulted in improved disease resistance in crops such as barley, rice, cassava, sugarcane, and com (Plotkin 1986). Thus, the loss of habitat and the possible extirpation or extinction of plant and animal species may mean the loss of potential life-saving drugs and crop-enhancing wild relatives.
- Dominance/Suppression Competitive Relationships in Loblolly Pine (Pinus taeda L.) PlantationsDyer, Michael E. (Virginia Tech, 1997-11-13)Data from three long-term field studies with loblolly pine (Pinus taeda L.) plantations were used to examine inequality (Gini coefficient) trends in diameter and the relationship between diameter relative growth rate (r) and initial size. Analysis with two spacing studies shows inequality increases with increasing density. For a given initial density, inequality initially decreases and then begins to increase as trees compete for resources. The slope of the linear relationship between r and relative size also increases with increasing density. The slope is initially negative and switches to positive as competition intensifies. The switch in the slope of the r/size relationship occurs when the crown projection area exceeds 1.05 or when the crown ratio falls below 0.75. These results are consistent with the resource pre-emptive or dominance/suppression theory of intra-specific competition. The r/size trends are not evident when calculations are based on class means as opposed to individual trees. The slope of the r/size relationship is a function of stand height, density, and to a lesser extent, site quality. Density reduction through mid-rotation thinning tends to decrease the slope coefficient. The r/size trends are used to develop a disaggregation model to distribute stand-level basal area growth over an initial tree list. This approach compares well with two other disaggregation models but tends to over predict growth on the largest trees.
- Ecological Impact of Glaze Storm Damage in an Appalachian Oak ForestWarrillow, Michael P. (Virginia Tech, 1999-02-02)Glaze damage to canopy trees, gap size and seedling regeneration was surveyed relating to site topographic features after a major glaze storm at Fishburn Forest in the central Appalachian mountain region. The survey sites were stratified according to aspect and landform, and sample plots were randomly assigned to each topographic category. The canopy trees in the plots were tallied and their damage was visually classified. The results demonstrated that different species had different susceptibilities to glaze damage and susceptibility of species varied as topography changed. Virginia pine was the most susceptible species. In general, trees had the greatest damage on steep slopes and eastern aspects, and least damage on toe-slopes. Some species varied greatly in their susceptibility to glaze damage across the topographic categories, such as red maple, while some species varied little, like blackgum. Basal area was reduced 6% and varied due to species and topography. Where glaze damage was severe, gaps in the forest canopy were created. Gap sizes and the effects of gap size and topography on seedling regeneration within gaps caused by glaze damage were assessed. Seedlings were tallied by species and height in microplots within each sample plot and in the nearest gap, where gap size was measured. Gap size varied from 14,000 m2 to less than 20 m2. Average gap size was 255 m2. Canopy tree damage, forest type and topography were the most important factors affecting gap size. Gaps tended to be larger on steep backslopes. Common seedling species in both gaps and understory were sassafras, serviceberry and red maple. Disturbance affected both seedling height and density, as did topography. However gap size had effect only on seedling height. The future forest in this area is unlikely to change significantly, as species composition of seedlings was largely unaffected by the glaze storm damage.
- Ecology and Control of Rhododendron (Rhododendron ponticum L.) in Turkish Eastern Beech (Fagus orientalis Lipsky) ForestsEsen, Derya (Virginia Tech, 2000-06-28)Purple-flowered rhododendron (Rhododendron ponticum L.) and yellow-flowered rhododendron (R. flavum Don.) are two dominant shrub species of the eastern beech (Fagus orientalis L.) understories in the eastern and western Black Sea Region (BSR), respectively. These invasive woody species significantly reduce beech growth and can preclude tree regeneration. The ecological consequence is an aging beech overstory with little or no regeneration to replace the mature trees. Great rhododendron (R. maximum L.) has been increasing in the forests of the Southern Appalachians of the United States, reducing tree regeneration and growth. The BSR and Southern Appalachians bear noteworthy similarities in climate, topography, and the forest flora. Purple-flowered and great rhododendrons also show important similarities in their ecology and the forest vegetation problems they can cause. Current rhododendron-dominated and threatened BSR forests may provide an advanced ecological picture of the forests of the Southern Appalachians in which great rhododendron now thrives. Therefore, new information gained on the ecology and effective and cost-efficient control of purple-flowered rhododendron may significantly improve forest management practices, not only for the current rhododendron-invaded BSR ecosystem, but also for other parts of the world. This dissertation consists of five separate yet related chapters. The first gives relevant literature reviewed for the dissertation. The second chapter focuses on various environmental and disturbance factors that may have shaped the current purple-flowered rhododendron-dominated beech forests of the BSR of Turkey. Chapter 3 assesses the effects of various manual and herbicidal woody control techniques on purple-flowered and yellow-flowered rhododendron in two field experiments in the BSR. The fourth chapter relates a study of uptake and translocation behavior of triclopyr ester and imazapyr in great rhododendron. This information is used to determine the optimum herbicide-surfactant combinations for the greatest active ingredient uptake and root translocation in great rhododendron. The last chapter is a synthesis of the information gained in all of these different experiments.
- Effect of Minimum Suppression and Maximum Release Years on Compression Parallel to Grain Strength and Specific Gravity for Small-sized Yellow-poplar (Liriodendron tulipifera L.) SpecimensMettanurak, Thammarat (Virginia Tech, 2008-04-04)Several researchers have concluded that there is little or no relationship between specific gravity and ring width or growth rate in yellow-poplar (Liriodendron tulipifera L.). Because most mechanical properties of wood are also closely related to specific gravity, it would thus be of interest to learn how minimum suppression and maximum release years' evidence that can be extracted from radial growth patterns based on a modified radial growth averaging (RGA) technique's influence the compression parallel to grain strength and specific gravity of wood. This study is designed to evaluate the effects of growth suppression and release on ultimate crushing stress and specific gravity for small-sized yellow-poplar specimens. Additionally, the relationship between specific gravity and ultimate crushing stress is investigated. Twenty-three yellow-poplar cores were examined for their growth ring widths. Minimum suppression and maximum release years were identified based on the modified RGA criteria method. From each increment core, three 1 Ã 1 Ã 4 mm specimens from both minimum suppression and maximum release years were tested for their ultimate crushing stresses using a micro-mechanical test system. The specific gravity of each specimen was also recorded. These data were analyzed using a paired samples t test and a simple linear regression. The results indicate that the mean ultimate crushing stress and specific gravity of maximum release years were significantly higher than that of minimum suppression years. Furthermore, the ultimate crushing stress was linearly related to the specific gravity of the specimens.
- Effect of season of harvest and site quality on hardwood regeneration on the Virginia PiedmontKays, Jonathan (Virginia Tech, 1985-03-05)Many existing Piedmont hardwood stands are composed of trees that are largely under 45 cm in diameter and contain a desirable oak component, as well as large amounts of undesirable red maple and sourwood. In stands under even-aged silviculture, season of harvest can be used as an effective management tool to favor different species compositions. If oak or other hardwood production is the management objective a dormant season harvest will result in increased sprout vigor of all oak as well as non-oak species. If pine conversion is the objective then a growing season harvest will reduce the vigor of all hardwood species and allow for easier competition control. The higher densities of all classes of regenerants on better sites indicates control will be more difficult.
- Effectiveness of Treatments to Reduce Rhododendron maximum and Promote Tree Seedling Regeneration in the Southern AppalachiansPearce, Christopher Deane (Virginia Tech, 2009-03-05)Rosebay rhododendron (Rhododendron maximum L.) is an evergreen ericaceous shrub that plays a dynamic role in the southern Appalachian forests. Commonly located on mesic sites, this understory shrub forms dense thickets that greatly reduce the amount of light available to herbaceous and woody plants found on the forest floor. Past research has shown that silvicultural methods can be used to eradicate R. maximum, however it is unclear which of these methods is most efficient and what effects other than stem mortality may occur. In this study, treatments involving prescribed fire, mechanical cutting, and herbicide applications were applied to R. maximum dominated forests in southwestern Virginia to determine what effect seven different silvicultural treatments had on 1) controlling of R. maximum as a forest weed 2) fuel loading inside of a R. maximum thicket, and 3) canopy tree seedling regeneration. Mechanical cutting treatments were successful in reducing R. maximum basal area per acre; however stump sprouting and increased fuel loading occurred. Herbicide applications were successful in controlling only the smallest diameter class of R. maximum stems. Prescribed fire reduced litter layers and caused delayed mortality on R. maximum stems three years following treatment. Hemispherical photographs taken within each plot showed that silvicultural treatments that successfully increased the amount of light entering each plot were influential in seedling establishment three years following treatments. Results from this study can be used to further perfect silvicultural applications that alleviate R. maximum cover on the forest landscape.
- Effects of alternative silvicultural practices on oak regeneration in the southern AppalachiansLorber, Jean Herault (Virginia Tech, 2003-06-05)The regeneration in oak-dominated stands following five silvicultural treatments was examined on four sites in the mountains of Virginia and West Virginia. Treatments included: silvicultural clearcut, leave-tree, commercial clearcut, shelterwood, and group selection. The effects of harvesting were compared among sites and among treatments. Oak regeneration dominance, measured by the relative density of dominant and codominant oak regeneration, was the most important variable calculated from the data. Oak regeneration dominance varied by site, but did not vary by silvicultural treatment; all treatments resulted in relatively low numbers. Therefore, the silvicultural treatments used here were not enough to overcome the site specific limitations to successful oak regeneration. Oak species also seemed to be less important in the regenerating stands than in their parent stands. The biggest losses in oak importance occurred on the intermediate and high quality sites; competitive oak regeneration was relatively scarce on two of the three sites with an oak site index (base age 50) of over 70 ft. Multiple linear regression analysis was used to identify the factors controlling oak regeneration at a smaller scale. The most important variables were those that described the oak stump sprouting potential, the understory and overstory oak component in the pre-harvest stand, post-harvest light and soil nitrogen levels.
- Effects of Clearcutting with Whole Tree Harvesting on Woody and Herbaceous Plant Diversity After 17-Years of Regrowth in a Southern Appalachian ForestWright, David Kenyon (Virginia Tech, 1997-12-15)This study examines the effects of clearcut regeneration with whole-tree harvesting on plant diversity. Three approaches were used to study changes in species composition and structure: (1) forest level, (2) stand level, and (3) diversity indices. Within each approach the forest was stratified into three horizontal vegetative regions based upon height: herb (< 1 m), shrub (between 1 and 5 m), and tree (> 5 m). Between the pre-harvest and 17-year-old forest, the relative percent cover of 3 out of 45 herbaceous and 2 out of 34 woody species were found to be significantly different (df = 3; a = 0.10) in the herb stratum; the importance value (average of relative basal area and stem density) of 2 out of 25 woody species in the shrub stratum; and 1 out of 21 woody species in the tree stratum. Within stands, the three lower quality, 17-year-old stands (SI50 = 12.2, 15.2, and 18.3 m) most resembled their pre-harvest composition; however, increases in ericaceous species were observed in the herb and shrub strata potentially inhibit the future regeneration of tree species. The SI50 = 21.3 m stand incurred the greatest changes in composition potentially due to the lack of fire as a disturbance mechanism. The major mechanism that has caused the shifts in species composition and structure is the change in the microenvironment due to the removal of the overstory, which has shifted the competitive advantages from one species to another. In all cases, diversity indices were not found to be significantly different between the 17-year-old and pre-harvest forests. Diversity indices were therefore determined to have limited use if a manager wants to know specific compositions and/or abundance of species.
- Effects of European Gypsy Moth Defoliation in Mixed Pine-Hardwood Stands in the Atlantic Coastal PlainDavidson, Christopher Bryn (Virginia Tech, 1997-10-28)As populations of the European gypsy moth (Lymantria dispar L.) move into the southeast, laboratory studies indicate that the potential exists for defoliation and possible tree mortality in mixed pine-hardwood stands. This dissertation describes a field study that was initiated to determine the susceptibility and vulnerability of pure and mixed stands of loblolly pine, oaks and sweetgum in pine-oak and pine-sweetgum cover types in the Atlantic Coastal Plain physiographic province. Sixteen stands were defoliated between 1992 and 1996. Stand susceptibility was significantly related to stand composition; stands with a greater proportion of susceptible species experienced greater defoliation. Oaks and sweetgum were heavily defoliated. Pines did not suffer extensive defoliation, and results of the study indicate that the probability of widespread gypsy moth defoliation in pine plantations appears to be low. A multiple linear regression model for the prediction of mean stand defoliation is also presented. Trends in tree mortality were similar to those previously described in northeastern forests. Susceptible tree species were heavily impacted, however, oaks displayed greater vulnerability than sweetgum. Suppressed and intermediate trees in the understory, and trees that were in poor or fair condition, had a greater probability of dying subsequent to defoliation. However, under- and overstory basal area mortality rates were not significantly different in the pine-oak type, and stem mortality rates were not significantly different in either type. Loblolly pine mortality was observed, but it was difficult to isolate the source, and thereby determine whether gypsy moth defoliation was a primary causal factor. In general, the potential for extensive pine mortality in mixed pine-hardwood stands does not appear to exist. Logistic regression was found to be a useful tool in the prediction of individual tree mortality and two logistic regression equations were derived and validated for use in pine-oak and pine-sweetgum cover types.
- Effects of hydrology-altering site preparation and fertilization/release on plant diversity and productivity in pine plantations in the coastal plain of VirginiaHauser, James W. (Virginia Tech, 1992-08-15)Biological diversity, or biodiversity, is declining on a global scale at unprecedented rates. These declines are largely the result of human activities and resource use. Intensive forestry is often cited as a contributing factor in biodiversity declines. Because forestry practices are being placed under increased scrutiny with respect to biodiversity impacts, the objective of this project was to determine the effects of specific silvicultural practices on plant diversity in pine plantations on wet flats in Virginia. The study area consisted of three sites in the Coastal Plain. The sites were originally established in 1969 to study the effects of various treatments on loblolly pine growth. The three treatments applied were chop and burn, bedding, and ditching. Fertilization subplots of P, N and P, N, P, and lime, and a control were added to the treatment areas in 1978. This study was conducted in 1991 when stands were 23 years old, nearing rotation age. Bedding exerted the greatest effect on plant diversity. Diversity was lower on the bedded treatment, although total biomass was higher. Bedding appears to increase pine growth by providing seedlings with more available soil volume and by reducing the vegetative regeneration of hardwoods and shrubs, thereby decreasing site diversity. Ditching likewise increased pine growth by lowering water table levels, but ditching had little effect on plant diversity. Fertilization exhibited only minor effects on diversity, and those effects that were observed did not reveal any definitive trends. Of the treatments applied, liming appeared to increase pine growth most, possibly due to increased calcium availability. Water table level was highly correlated to mid story diversity, though it was less correlated to other canopy layers. In addition, correlation analyses indicated a significant degree of interaction between canopy layers. It appears that diversity, particularly in the lower canopy layers, is affected directly by treatments and indirectly by shifts in overstory characteristics. Intensive forest management involving hydrology-altering site preparation and fertilization impacted plant diversity within these wet flat plantations. Whether such changes affect wildlife habitat or ecosystem functioning requires further study.
- Effects of Low-Input Vegetation Management on Pine-Hardwood Mixed Stands in the Northern PiedmontHeinze, Jason A. (Virginia Tech, 1999-11-05)In an attempt to provide low-cost, low-input alternatives for regenerating pine-hardwood mixtures, this study examined several mechanisms that influence the growth of pine-hardwood stands. The Regeneration Alternatives Study is an ongoing experiment that was designed to gain biological and economical information concerning the growth and yield of loblolly pine and mixed hardwood species. Low-cost herbicide applications (stump treatment, basal stem spray, release, and soil spot release) were used to control competing vegetation during the study. The four even-aged regeneration treatments applied to loblolly pine and mixed hardwood stands of this study had a significant effect on their growth. Loblolly pine growth increased and mixed hardwood growth decreased as the intensity of herbicide treatment increased for all age classes. In general, loblolly pine was more productive with more intense treatment applications on poorer sites following a growing season harvest. Hardwood species were more productive with less intense treatment applications on higher-quality sites following a dormant season harvest for all age classes. Loblolly pine planting following clearfelling, coupled with a herbicide stump and release treatment (treatment 4), resulted in the highest yields of loblolly pine, the greatest economic returns, and the greatest level of site utilization. However, treatment 4 also resulted in the lowest yield of mixed hardwoods and the lowest level of species richness. Loblolly pine planting following clearfelling, with (treatment 3) and without (treatment 2) a hardwood stump treatment application, resulted in a more even distribution of pines and hardwoods, depending on the treatment. Treatment 3 favored loblolly pine growth, especially following a growing season harvest on poor sites. Treatment 2 favored mixed hardwood growth, especially following a dormant season harvest on good sites. There were no differences between methods of release (basal spray or soil spot herbicide application). Economically, treatments 2 and 3 did not realize a profit on returns. Pine yields, dbh, and basal area were all significantly greater following a summer season harvest as opposed to pine growth following a winter harvest with the same chemical treatments. The pine growth data indicated that less intense chemical treatments following a summer harvest can achieve the same or greater growth results than more intense chemical treatments following a winter harvest. The results of this study indicate a significant biological and economic tradeoff, depending on the level of hardwood control applied and the time of harvesting.
- Effects of Mid-Rotation Release on Forest Structure, Wildlife Habitat, and Pine YieldCheynet, Kyla Ingeborg (Virginia Tech, 1999-11-30)The effects of two forms of mid-rotation release on thinned, fertilized loblolly pine (Pinus taeda L.) plantations in Virginia were examined: aerial imazapyr and basal triclopyr application. Imazapyr measurement plots were installed in nine Piedmont and twelve Coastal Plain plantations operationally released with imazapyr, and triclopyr measurement plots were installed within a controlled fertilization/release study spanning both regions. No differences in volume were detected following triclopyr release. All release dates combined, Piedmont released areas averaged 0.06 m3/tree (18%) greater than the control and Coastal Plain released areas averaged 0.05 m3/tree (14%) greater than the control. Reductions in hardwood basal area, stem density, and shrub stratum cover were observed for both forms of release. Reductions in shrub stratum richness and diversity were also documented for imazapyr release; however, trends indicate that richness and diversity, as well as stem density and shrub stratum cover, may recover to pre-treatment levels. Herbaceous vegetation was increased on triclopyr sites, which was reflected in an elevated turkey (Meleagris gallopavo sylvestris L.) food/brood index. Following imazapyr release, habitat suitability index (HSI) values for pine warblers (Dendroica pinus L.) and black-capped chickadees (Parus atricapillus L.) increased due to reductions in canopy hardwoods and increases in snags. Reduced shrub stratum density resulted in a lower bobwhite quail (Colinus virginianus L.) cover index on imazapyr-released areas.